I've found Gray's Papaya to be more consistent and better overall. I wouldn't say either are amazing, but it's hard for hot dogs to be amazing (Hot Doug's in Chicago being a notable exception). You might be disappointed if you're treating it as a destination place, but Gray's is among the best cheap hot dogs in Manhattan, and it's hard to complain about paying less than $5 for 2 natural-casing hot dogs and a fruit drink.